Effect of passively aerated biological pretreatment on different biomasses with diverse lignocellulosic fiber profiles

Abstract

Passively aerated biological pretreatment was applied to four different lignocellulosic biomasses with varying fiber content profiles: sugar beet pulp (SBP), brewery bagasse (BB), rice husk (RH), and orange peel (OP). In order to analyze the organic matter solubilization yield at 24 and 48 h, different percentages of activated sewage sludge (2.5–10%) were utilized as inoculum. The OP achieved the best organic matter solubilization yield in terms of soluble chemical oxygen demand (sCOD) and dissolved organic carbon (DOC) at 2.5% inoculation and 24 h: 58.6% and 20%, respectively, since some total reducing sugars (TRS) consumption was identified after 24 h. On the contrary, the worst organic matter solubilization yield was obtained with RH, the substrate with the highest lignin content among the tested, with percentages of 3.6% and 0.7% in terms of sCOD and DOC respectively. In fact, it could be considered that this pretreatment was not successful with RH. The optimum inoculation proportion was 7.5% (v/v) except for the OP (2.5% (v/v)). Finally, due to the counterproductive organic matter consumption at longer pretreatment durations, the optimal time for BB, SBP, and OP was 24 h.